Electric light source



June 30, 1936. sp

ELECTRIC LIGHT SOURCE Filed Jan. 22, 1931 JVVENTOR. 62.

ATTORNEYS Patented June 30, 1936 UNITED STATES PATENT OFFICE and mesne assignments, to Sperti Lamp Corporation, New York, N. Y., a corporation of Delaware I Application January 22, 1931, Serial No. 510,412

10 Claims.

This invention relates to electric light sources and particularly to electric light sources which combine both visible and ultra-violet radiation to produce a spectrum closely resembling that of natural sunlight.

Investigations made during recent years have shown definitely that ultra-violet light has valuable therapeutic properties and this knowledge has resulted in considerable development of ultra-violet lamps for therapeutic purposes. Such lamps however are of the character of curative or remedial agents, to be used for prescribed treatments under the direction of a physician; as a rule they embody a mercury arc and accordingly are deficient in the yellow and red rays of the spectrum and are not adapted for general illumination purposes. It has also been attempted to provide a single lamp embodying an arc in mercury or other vapor supplemented by a source of radiation rich in yellow and red rays so that the light from the lamp provides a white light suitable for general illumination. For example, it has been proposed to operate an arc between tungsten electrodes in an atmosphere of mercury or other vapor together with an incandescent filament of tungsten or the like. Such lamps, however, have not been adapted for operation at normal house lighting voltages and currents so that their use has been restricted to special installations or to use with auxiliary equipment such as transformers.

In my application Serial No. 564,907 filed September 24, 1931, a continuation of my applications Serial Nos. 368,249 and 368,250 filed June 4, 1929, there is disclosed a general purpose lamp which can be used in the ordinary electric lamp socket for all the purposes to which the usual incandescent lamp can be put and which provides a white light suitable for general illumination and containing ultra-violet radiation as in the case of natural sunlight. This lamp embodies a bulb containing mercury or other vapor, resistance means connected in series across the leads of the lamp and radiating in the visible portion of the spectrum, the filament being enclosed and kept out of contact with the vapor, and electrodes connected with the resistance means so that an arc is established in parallel with the filament. This lamp can be used in place of or in addition to existing light sources without auxiliary equipment or any special manipulation in starting. The filament and the vapor are are stable and permanent in the presence of each other and the lamp is self-contained in the sense that it does not require external controlling, starting, or balancing devices.

It is known that the beneficial portion of the ultra-violet spectrum is limited to radiations of wave lengths longer than a limit in the neighborhood of 2,950 to 3,000 angstrom units and that shorter radiations may produce harmful effects. Natural sunlight under good conditions does not containradlations of wave lengths shorter than 2,950 or substantially 3,000 angstrom units which accounts for the beneficial results obtained by exposure to sunlight and for the absence of harmful effects. Since so much time is now spent under artificial illumination it is desirable to provide electric light sources which reproduce as nearly as possible the sun spectrum in order to obtain the benefits of ultra-violet radiation while excluding the objectionable short wave lengths below substantially 3,000 angstrom units as above stated.

One of the objects of this invention is to provide a novel electric light source having the general characteristics of the lamp disclosed in my aforesaid application Serial No. 564,907, producing both visible and ultra-violet radiations and having means for eliminating the objectionable short wave length energy.

Another object is to provide a novel light source of the above type wherein the visible radiation is produced directly by an incandescent tungsten or other filament enclosed in a translucent envelope to prevent access of the mercury or other vapor thereto.

A lamp embodying the invention comprises a suitable bulb or envelope of material translucent to the desired radiations and enclosing an incandescent light source and a second light source which is a mercury or other vapor are or an electrical discharge through a rarified or ionized gas. In order to prevent disintegration of the filament in the presence of the arc, the same is enclosed or sealed within a translucent envelope of glass or other suitable material and the arc electrodes are separate from the filament but in electrical connection therewith so that the potential drop through the filament is impressed across the electrodes.

One embodiment of the invention has been illustrated in the accompanying drawing, but it is to be expressly understood that said drawing is for purposes of illustration only and is not to be construed as a definition of the limits of the invention, reference being had to the appended claims for this purpose.

Referring to the drawing, the sheath, envelope or bulb l of the lamp is of translucent material, the characteristics of which are hereinafter more fully described. This bulb is fitted with terminal connections of a commonly accepted type; as shown, the base for the bulb comprises the usual threaded sheath or screw cap 2, provided with a central contact button 3, so that the lamp may be screwed into the ordinary receptacle. Fixed within the bulb are supporting members 4 and 5, which are of insulating substance and may conveniently and cheaply be made of glass. These supports are hollow, and through thempass lead wires 6 and I. At the ends of these supports are electrodes 8 and 9, which are of any suitable shape. As shown they are of rod-like or cylindrical shape, and they have the characteristic of adsorbing mercury. Electrodes of zirconium oxide are suitable, but a large number of other refractory oxides may be employed, as well as substances which contain refractory oxides in combination with other materials. Thus porcelain may serve. The electrodes should, of course, be electrically conductive at least when highly heated or obviously they will not serve as electrodes for the arc. Zirconium and other refractory oxides, however, have this property.

Electrical contact is made between the lead wires 6 and 1 and the electrodes 8 and 9, and as shown wires [0 and H passing through the central portion of the electrodes not only make electrical contact with the electrodes, but are preferably filaments having a heat producing characteristic whereby the electrodes may be heated up to ionize the mercury atmosphere, thereby starting the arc, and to render them conductive so that the arc may pass. If desired electrodes 8 and 9 may be made hollow to more easily accommodate filaments Ill and II. I

The electrodes may be fused into the supports 4 and 5, and in such case it is preferable to make these supports of some substance the co-eflicient of expansion of .which is substantially the same as the co-eflicient of expansion of the substance of the electrodes. Quartz has substantially the same co-eflicient of expansion as zirconium oxide, and there is a glass, commercially obtainable, which likewise has the same co-eificient of expansion. It will be understood however that the electrodes may be secured to the supports 4 and 5 in any suitable manner other than by fusing.

The filaments I0 and H are connected by a filament H, which in this instance is an illuminating filament, adapted to give light of a pleasing character in the visible spectrum, and particularly such light as will enrich the light of the mercury vapor are (if an arc of mercury vapor alone is used) in the portions of the visible spec trum in which it is lacking. A filament such as is used in ordinary incandescent lamps is excel lent here. This filament is protected from the atmosphere of vapor inside the bulb or sheath I by a sheath or tube of insulating material l3. This material is translucent, but since the function of the filament is primarily to emit light in the visible spectrum, this sheath need not necessarily be of material translucent to ultra-violet light. Quartz glass is thus unnecessary in the sheath I3, and so are those special glasses which are translucent to ultra-violet light. The ends of the sheath will be connected to the ends of the electrodes 8 and 9 in any suitable manner so that the filament I2 will be sealed against the access of vapor. The tube or sheath may be evacuated; and where it is oi! other than straight construction, the filament may be held onone or more suitable supports l4 carried by the sheath.

The exact construction shown may be greatly modified. The electrodes need not form part of the general supporting structure, but may be sup- 5 ported externally upon or independently of the sheath, tube or separate vessel containing and protecting the filament. In this case electrical contact with the electrodes at the proper points in the circuit must be separately made.

The character of the filament I2 is such as to produce a suificient voltage drop between electrodes to permit the passage of the arc. In an ordinary construction designed to operate on 110 volts, the voltage drop across the filament may 15 be in the neighborhood of to volts.

For the control of the arc, one or more ballast resistances may be employed in series with the arc path between the electrodes. In the form shown, ballast resistances l5 and I6 are inserted 20 in the leads 6 and I, which leads beyond these resistances are connected respectively with the screw sheath 2 and with, the contact button I of the base. The ballast resistances l5 and I6 constitute an additional source of visible light, and 25 the relative amounts of visible light provided by the filament l2 and by the ballast resistances l5 and I6 depend upon the proportioning of the resistances in the circuit and on the voltage drop across the are. Where the voltage drop in the 30 are is low the drop through the filament l2 will be correspondingly low and the ballast resistances l5 and I6 may provide the greater part of the visible light.

A quantity oi, mercury I! may, if necessary, 35 be placed in the bulb l to supply additional vapor for the arc, and other materials may be used or mixed with mercury so as to provide other characters of illumination. As explained, the electrodes 8 and 9 are of such character that as they 40 cool off after a period of operation of the are,

- they will adsorb mercury. When the current is turned on in the lamp, the electrodes 8 and 9 will be heated and rendered conductive by this heat and mercury ions will be driven off from them and ionized sufllciently to allow the arc to start. Ordinarily this quantity of mercury will be sumcient to maintain the are, but additional mercury vapor may be supplied by the vaporization of the mercury H.

The envelope or bulb l is of material translucent to ultra-violet as well as visible rays, since the purpose of the arc is to produce a useful quantity of such rays. Quartz or any of the ultraviolet transmitting glasses are suitable; but where the lamp is to be used for the lighting of houses, ofiices, hospitals and the like, it is preferable to employ a substance for the envelope which will have a sharp cut-off point in the ultra-violet region around 3,000 angstrom units. It has been 60 shown that ultra-violet radiations longer than substantially 3,000 A. U. are of great benefit to living organisms, but have none of the deleterious efiects heretofore noted in connection with full ultra-violet irradiations. Instead of forming 5 the envelope of such a substance it way be coated with a filtering material.

While only one embodiment of the invention has been described and illustrated in the drawing, it will be understood that the invention is not lim- 70 ited to this embodiment. Any suitable materials may be employed for the electrodes, tube l3 and bulb' l. The bulb I may have any desired shape and the base 2 may be replaced by a base of an known type. In some instances the stabiliz- 75 envelope connecting said electrodes including an ing resistances may be unnecessary and can then be omitted. The arc may be operated in mercury or in any other vapor producing the desired radiations. These and other changes, such as in the form, details of construction and arrangement of parts, can be made without departing from the spirit of the invention and reference is therefore to be had to the appended claims for a definition of the limits of the invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent. is:-

1. A lamp comprising a bulb transmitting both ultra-violet and visible radiation, a base for said bulb including a pair of terminals, a pair of leads connected to said terminals, a tube supported within said bulb with its ends connected to said base and receiving said leads, spaced portions of said tube being formed of refractory oxide material and another portion being of a translucent material, said refractory oxide portions constituting arc electrodes, a quantity of ionizable material in said bulb, resistance heating means housed within and in electrical contact with said refractory oxide portions, incandescible resistance means housed in said translucent portion and constituting a source of visible light, and means connecting all of said resistance means in series with said leads.

2. A lamp comprising a bulb transmitting both ultra-violet and visible radiation, a base for said bulb including a pair of terminals, a pair of leads connected to said terminals, a tube supported within said bulb with its ends connected to said base and receiving said leads, spaced portions of said tube being formed of refractory oxide material and another portion located between said refractory oxide portions being of a translucent material, said refractory oxide portions constituting arc electrodes, a quantity of ionizable material in said bulb, resistance heating means housed within and in electrical contact with said refractory oxide portions, incandescible resistance means housed in said translucent portion and constituting a source of visible light, and means connecting all of said resistance means in series with said leads including ballast resistance means interposed between said leads and at least one of the points of connection between said heating resistances and the refractory oxide electrodes.

3. A light source comprising an outer envelope translucent to visible and ultra-violet radiations of wave lengths found in sunlight but opaque to radiations of shorter wave lengths, a pair of leads for said source, a pair of spaced hollow electrodes, a quantity of ionizable material, resistance heating elements within said electrodes and electrically connected therewith, an inner translucent envelope within said outer envelope, an incandescent filament and a ballast resistance enclosed in one of said envelopes, said filament, resistance heating elements and ballast resistance being connected in series across said leads, said electrodes and ionizable material being enclosed in the other of said envelopes.

4. A light source comprising an envelope translucent to visible and ultra-violet light and provided with a pair of terminals, a pair of supports of insulating material within said envelope, conductors housed within said supports and con nected to said terminals, a pair of electrodes attached to said supports and electrically connected to said conductors, an envelope of translucent material secured to and connecting said electrodes, and a conductor in said last named incandescent filament adapted to produce light in the visible spectrum continuously during operation of the source.

5. A light source comprising an envelope translucent to visible and ultra-violet light and provided with a pair of terminals, a pair of supports of insulating material within said envelope, conductors housed within said supports and connected to said terminals, a pair of electrodes for an are attached to said supports and electrically connected to said conductors, an envelope of translucent material secured to and connecting said electrodes, a conductor in said last named envelope connecting said electrodes including an incandescent filament adapted to produce light in the visible spectrum continuously during operation of the source, said electrodes being of a refractory oxide material, heating means for said electrodes in the series circuit with said filament, and a quantity of mercury in said first named envelope.

6. A light source comprising an envelope of material translucent to visible and ultra-violet light, a pair of terminals for said source, a pair of supports of fusible insulating material in said envelope, arc electrodes of refractory oxide fused into said supports, a tube of insulating fusible translucent material connecting said electrodes and fused thereto, an incandescent filament in said tube adapted to produce light in the Visible spectrum continuously during operation of the source, a series circuit between said terminals including stabilizing resistances and said filament, said electrodes being connected to said circuit on either side of said filament, and a quantity of mercury in said envelope.

7. A light source comprising an envelope of material translucent to visible and ultra-violet light, a pair of terminals for said source, a pair of supports of fusible insulating material in said envelope, arc electrodes of refractory oxide fused into said supports, a tube of insulating fusible translucent material connecting said electrodes and fused thereto, an incandescent filament in said tube adapted to produce light in the visible spectrum continuously during operation of the source, a series circuit including said terminals, stabilizing resistances and said filament, said electrodes being hollow and provided within with heating filaments connected in series in said cir- .cuit, and a quantity of mercury in said envelope.

8. A light source comprising an outer envelope translucent to visible and ultra-violet radiations of wave lengths longer than substantially 3,000 angstrom units but opaque to radiations of substantially shorter wave lengths, a pair of leads for said source, a pair of spaced hollow electrodes, a quantity of ionizable material, resistance heating elements within said electrodes and electrically connected therewith, an inner translucent envelope within said outer envelope, and an incandescent filament enclosed in one of said envelopes, said filament and resistance heating elements being connected in series across said leads, said electrodes and ionizable material being enclosed in the other of said envelopes.

9. In a lamp embodying a source of ultra-violet radiations and a source of visible light, an envelope translucent to ultra-violet radiations and containing a quantity of ionizable material, a pair of spaced, substantially parallel sections of tubing within said envelope, one portion of each of said sections being formed of refractory oxide and another portion of translucent material,

heating coils within and in electrical contact with the inner surfaces of said oxide portions, resistance means housed within said translucent portions and constituting sources of visible light, and means connecting said heating coils and resistance means in series.

win a lamp embodying a source of ultraviolet radiations and a source of visible light, an envelope translucent to ultra-violet radiations and containing a quantity of ionizable material, a pair 0: spaced, substantiaiiy parallel sections of tubing within said envelope, one portion of each of said mtions being formed of zirconium oxide and another portion of translucent material, resistance coils within and in electrical contact with said zirconium oxide portions, in= candeseent filament means within said translucent portions. and means connecting said rei sistance coils and incandescent filament means in series.

GEORGE SEERTI. 10 

